a) Field of Invention
This invention relates generally to multiple-pane sealed glazing units and more particularly to units that incorporate decorative features that simulate the appearance of traditional divided-lite windows.
b) Description of the Prior Art
In U.S. Pat. No. 5,494,715, issued to Glover, there is a description of the various efforts that have been made in recent years to improve both the energy efficiency and condensation resistance of multiple glazed sealed units. These improvements include: low-e coatings, argon or krypton gas fill, insulating spacingand-desiccant systems for perimeter edge seals and narrow-width cavities (approximately 3/8" spacing for argon gas filled units).
As also noted in U.S. Pat. No. 4,494,715, there is a growing consumer interest in heritage window features. Perhaps the most popular of these features is the addition of muntin bars that create the appearance of colonial style divided-lite windows. In the past, various efforts have been made to simplify the assembly of these divided-lite windows and these efforts have been documented in the patent literature.
U.S. Pat. No. 4,598,520 issued to Ellstrom describes the use of two separate but aligned wood muntin grid assemblies that are permanently adhered to either side of a multiple-pane sealed unit using double-sided adhesive foam tape. When viewed at a somewhat inclined angle, the visual illusion is created of a solid muntin-grid assembly. However, when viewed at a more oblique angle, this visual illusion is lost because daylight can be seen between the two muntin grid assemblies.
U.S. Pat. No. 4,738,938 issued to Palmer describes a muntin-grid window assembly similar to the assembly described in the Ellstrom patent but where an additional metal muntin-grid is also incorporated within the sealed unit. However, although the addition of a metal spacer muntin-grid better simulates the appearance of a divided-lite window, window energy efficiency is reduced because of increased heat loss through the muntin grid assembly.
U.S. Pat. No. 5,345,743 issued to Baier describes a muntin grid window assembly similar to the assembly described in the Palmer patent but where a flexible foam spacer with pre-applied adhesive is substituted for the metal spacer grid. Although more energy efficient than a simulated divided-lite window with a metal spacer muntin-grid, the double muntin grid assembly method still remains a labour intensive manufacturing process and the grid assembly is still a weak link in the thermal envelope.
U.S. Pat. No. 5,494,715 issued to Glover describes how the visual illusion of a muntin grid window is created by means of decorative stripe patterns that are applied to the three separate glazing sheets of a triple glazed unit with the glazing sheets being typically located no more than 3/8" apart.
Traditional wood muntins are typically colored white, and when all three muntin stripes are colored white, experience has shown that because of various shading and optical effects, a convincing visual illusion of a divided lite window is not always created. The decorative surface patterns can be fabricated from a wide range of materials, including inks and paints. Because of potential durability problems, the stripe material must be non-outgassing and with high volume production methods, experience has again shown that for typical coating materials, this is a very demanding technical requirement.